The present invention relates to the structure of a viewfinder of a thin-type camera whose transverse dimension, i.e., depth, is small, and more particularly to a viewfinder optical system which permits high magnification and zooming.
In recent years, various types of so-called digital camera have been proposed which effect recording and reproduction by photographing with a CCD element a subject image formed by a taking optical system. With this type of camera, since the imaging area of the CCD element is small, the focal length of the taking optical system for obtaining a standard angle of view also becomes short. Hence, since the optic-axial distance of the taking optical system can be made short, the dimension in the direction of the principal optical axis of the taking optical system, i.e., the depth of the camera, can be made small, and it is possible to configure a camera which is thin in its transverse direction. However, in a case where a direct-view finder is fitted in this type of camera, an arrangement is provided such that an objective window is disposed on the front surface side of the camera, and an ocular window is disposed on the rear surface side of the camera. Consequently, the optic-axial length of the viewfinder optical system also becomes short in conjunction with the trend toward the thinner camera, and the magnification of the viewfinder becomes small, with the result that the subject image is confirmed and the photographing range is confirmed while viewing a small subject image, making it impossible to effect satisfactory viewfinder confirmation.
In addition, among the above-described digital cameras in recent years, one which uses a zoom lens as its taking optical system has been proposed, and as its viewfinder optical system one having a zooming configuration capable of varying the magnification of the viewfinder in correspondence with the zoom magnification in the taking optical system is installed. With such a digital camera having the zooming configuration, if an attempt is made to make the camera thin as described above, the optic-axial length of the viewfinder optical system becomes short, which makes it difficult to realize a viewfinder optical system having the zooming configuration capable of realizing a zoom magnification and a zoom ratio which are desired.
Thus, with the conventional thin-type cameras, since a restriction is imposed on the optic-axial length of the viewfinder optical system, there are problems in that it is impossible to obtain a viewfinder optical system of a high magnification and a viewfinder optical system of a desired zoom magnification, and that, in particular, it is difficult to confirm the subject with a high magnification during shooting.